Well, after all, its a Ubisoft game... not working is part of their motto.!
Many of their games have had that problem, it appears that if you have a Virtual disc installed or if your CD Rom is a SATA CD Rom, UBI's DRM takes the CD Rom as a Virtual disc, aka pirated version, hence, the problem with not seeing the disc. Now, this is what was happening with games like GRAW, VEGAS, etc, so this was back in 2005 an on... you would think that by now that problem would be solved, right?
Things you could try.... if you haven't already
1.- Insert disc but do not let it autoplay or click on Explore Folder.
2.- In Explore Folder, right click on the setup.exe and Run as an Administrator
3.- if that does not work, try copying the content of the Disc onto a Temp folder in your HDD and try #2 again.
If after that brutal punishment the game still does not work, you can either... get your money back and be done with UBI or try your luck with their Tech Support but I gotta be honest, don't hold your breath with them.